Cosmetics contain powders or pigments for improving coloration, feeling and the like. In case that powders and pigments are to be used for these purposes, it is required that the powders and pigments should be uniformly dispersed in cosmetics (cosmetic compositions) to obtain cosmetics having high long-term dispersion stability without unevenness in color and the like. However, in case that ordinary powders or pigments are selected to be dispersed in aqueous dispersion media, there is a need to hydrophilize (make a hydrophilic treatment) them. Without hydrophilization (hydrophilic treatment), depending on the selection of various agent form, it is impossible to obtain cosmetics having good dispersibility and long-term dispersion stability and further having, when selecting aqueous cosmetics (cosmetics of aqueous type) as the agent form thereof, ready re-dispersibility (ease of re-dispersion) and long-term dispersion stability with lapse of time.
Alternatively, many proposals have been so far made for hydrophilicaly treating hydrophobic powders or pigments (refer to Patent Documents 1 to 5).
It is reported that in case of for example a dispersion prepared by dispersing a pigment excellent in water resistance and weatherability (weather resistance) into water using a surfactant, the pigment is stably dispersed in water by the surfactant, so that the pigment remains dispersed in a stable manner and does not precipitate in the system for a certain length of time (refer to Patent Document 1).
Furthermore, it is reported that an inorganic pigment hydrophilicaly treated (hydrophilized) by coating the inorganic pigment with a water-soluble polymer has good dispersibility in water and stable dispersibility (refer to Patent Document 2).
Still further, a pigment treated hydrophilicaly by coating the pigment with a nonionic surfactant of HLB 7 to 18 and a fatty acid soap has good dispersibility in water without any occurrence of precipitation or adhesion, even after use for a long period of time (refer to Patent Document 3).
However, the method of hydrophilic treatment (surface treatment) with the surfactant or the water-soluble polymer or the combination of the nonionic surfactant and the fatty acid soap is said to be hard in being satisfactory for dispersing hydrophobic powders or pigments in an aqueous dispersion medium. When the hydrophilicaly treated (hydrophilicaly-treated) powder is incorporated into cosmetics therewith, the powders or the pigments are dissociated or separated in the system, so that the powders or the pigments agglomerate. Consequently, this causes uneven color or a difference between color in appearance and color at the time of application therein or long-term dispersion stability with lapse of time is impaired, or in case of some form of cosmetics, the re-dispersibility of the powders or the pigments in the system may be worsened to cause caking and notably decreases its usability.
From the standpoints of heat resistance, water resistance, refractive index, coloration and the like, cosmetics contain, as a powder for cosmetics, a silicone resin or an organic powder (PMMA, nylon, polyester, polystyrene, cellulose, silicone elastomer powder, silicone rubber powder, benzoguanamine, styrenedivinylbenzene pinhole polymer, ethylene tetrafluoride, polyethylene powder, polypropylene powder, polyurethane powder, silk powder, metal soap powder, starch powder, N-acylated lysine, an organic pigment, and a composite of one or more of these organic powders with a metal oxide and/or a metal hydroxide) are blended as cosmetic powders in the cosmetics. It is very hard to disperse these powders (particles) in an aqueous dispersion medium by hitherto-proposed methods for hydrophilicaly treating hydrophobic powders or pigments.
For example, a powder which is hydrophilicaly treated with a silylating agent having a polyethylene chain is proposed, and it is reported that in case that this powder is incorporated into a nail enamel of an aqueous type along with an acrylic type polymer emulsion, a nail enamel of an aqueous type which is excellent in dispersion stability of a powder can be provided (refer to Patent Document 4).
Additionally, a hydrophilicaly treated pigment, in which a hydrophilic organic group is introduced into a pigment using a hydrophilic silane compound or silane coupling agent, and a composition containing the same is proposed (refer to Patent Document 5).
However, a pigment that is hydrophilicaly surface treated with polyethylene chain having a silylating agent is incorporated along with the above mentioned acrylic type polymer emulsion, and the above-mentioned hydrophilicaly surface treated pigment in which the hydrophilic organic group is introduced with the hydrophilic silane compound or silane coupling agent, do not satisfy the dispersibility or the long-term dispersion stability in various cosmetics systems. Accordingly, even when using a silicone resin and an organic powder with a strong hydrophilic property, the dispersibility in the system of the cosmetics and the long-term dispersion stability can not be satisfactory. The refractive index, transparency, the lubricity, the elasticity, the touch and the like which are effects provided by the silicone resin and the organic powder can hardly be exerted sufficiently.
In make-up cosmetics containing powders, for example, a cake type foundation, a humectant has been used to impart a moist feel for a smooth feeling, especially a smooth feeling after use to the skin. When cosmetics containing a humectant are applied on the skin, however, since the oil absorption or water absorption of the powder is too strong, the powder adsorbs the sebum or moisture, more than as required, from the skin. In other words, cosmetics containing a humectant lack a smooth feeling, especially a moist touch, and the use of a humectant in cosmetics causes an increase in a rough feeling or a dry feeling of the skin. When such cosmetics are applied on the skin, therefore, it provides a hard feeling to skin, but not a soft feeling. In addition, affixture of a powder contained in cosmetics to the skin is worsened, and adhesion of a cosmetic film on the skin is deficient. As the results of these, consequently, these defects have also caused the makeup to come off. Particularly, the rough feeling of the skin has been clearly problematic in winter.
In order to solve this problem, the addition of a humectant such as glycerin, propylene glycol or 1,3-butylene glycol to cosmetics has been attempted so far. When cosmetics containing a powder are produced by simply mixing a humectant with other ingredients, various ingredients are used as starting materials for cosmetics to be adhered to or adsorbed on the surface of the powder, and further the surface properties of the powder become heterogeneous, and the affixture to the skin decreases. Consequently, the rough feeling and the dry feeling of the skin cannot be improved, and the makeup is liable to come off due to secretion from the skin, the movement of muscles of facial expression, and the like. In addition, when the humectant is incorporated (mixed) along with the powder, the low-molecular part of the humectant is adsorbed on the powder, but the majority of the humectant is easily desorbed from the surface of the powder, so that a mere wetting phenomenon is shown. Thus, the humectant does not basically change the surface properties of the powder. Accordingly, it is impossible to decrease the rough feeling on the skin caused by the powder and improve the affixture to the skin, so that the moist touch cannot be improved and maintained. Moreover, the unevenness of the cosmetic film caused by the powder formed on the skin cannot basically be eliminated, thereby contributing to the makeup coming off the skin.
There is also a method in which affinity for water in a powder is increased by treating the powder with silica and alumina. However this method has been problematic in that the surface activity of the powder does not have sufficient dispersibility in water. Furthermore, in cosmetics containing the treated powder (silica- or alumina-treated powder), the powder itself and the surface-treating agent applied to its surface become separated or dissociated. Consequently, the powder aggregates in the system, or thereby a difference between the appearance color and application color is caused. In addition, depending on the different form of cosmetics, for example, in case of a cosmetic of bi-layer type, the powder might cause a caking phenomenon to notably decrease re-dispersibility and greatly impair usability.
In most of the methods for hydrophilicaly treating hydrophobic powders or pigments, which have been so far proposed, for example, by reason that a coated film on the powder is dissolved in an aqueous dispersion medium or cosmetics under acidic and alkaline conditions, especially in alkaline conditions, it is difficult to uniformly disperse the powder in the aqueous dispersion medium or cosmetics and maintain this dispersed state for a long period of time (refer to Patent Documents 6 to 8).
For example, a coated pigment is proposed in which a surface of an inorganic pigment is coated with a polyvalent metal salt of an anionic high-molecular compound, and it is reported that a makeup product containing the same, is excellent in its affixture to the skin and the like (refer to Patent Document 6).
A water-dispersible pigment is proposed in which a pigment powder (an inorganic pigment, an organic pigment, carbon or a resin powder pigment) is surface-treated with a specific alkoxysilane compound, and it is reported that such a pigment is easily dispersed in neutral water and is excellent in water dispersion stability over a long period of time and coating stability (refer to Patent Document 7).
Still additionally, a hydrophilicaly modified polyethylene of a high molecular weight is proposed, as prepared by treating a high-molecular polyethylene with a mixture of a water-soluble surfactant and a water-insoluble polyalkylene glycol. It is reported that such polyethylene has great stability for a long period of time and temperature-stability (refer to Patent Document 8).
Nevertheless, in the pigment coated with the polyvalent metal salt of the anionic high-molecular compound, the above water-dispersible pigment surface-treated with the specific alkoxysilane compound, and the polyethylene with the surface treated with a mixture of a water-soluble detergent and a water-insoluble polyalkylene glycol, the coated films on their surface are dissolved under alkaline conditions. Therefore, in cosmetics containing these hydrophilicaly treated pigments, similar to the above, for example, the pigments may be dissociated or separated in the system, and subsequently aggregated, and consequently create an uneven color or difference in color between appearance and at the time of application, or long-term dispersion stability with lapse of time may be impaired.
Accordingly, in a system in which the cosmetics (especially cosmetics of aqueous type) contain a surface-treated powder hydrophilicaly treated by the above conventional method of hydrophilic treatment, the surface-treated powder hydrophilicaly treated by the above conventional method of hydrophilic treatment aggregates, or the dispersion stability with lapse of time is impaired. Thus, the effects thereof are hardly exhibited satisfactorily. Especially, in most of surface-treated powders which are hydrophilicaly treated by the above conventional methods of hydrophilic treatment, the coated film of the powder is dissolved under alkaline conditions. Therefore, these problems are clearly seen in the system in which the powder is incorporated in alkaline cosmetics. Accordingly, it is desirable to develop a powder obtained (prepared) by hydrophilicaly treating the silicone resin and/or the organic powder (PMMA, nylon, polyester, polystyrene, cellulose, silicone elastomer powder, silicone rubber powder, benzoguanamine, styrenedivinylbenzene pinhole polymer, ethylene tetrafluoride, polyethylene powder, polypropylene powder, polyurethane powder, silk powder, metal soap powder, starch powder, N-acylated lysine, an organic pigment, and a composite of one or more of these organic powders described above with a metal oxide and/or a metal hydroxide) (particle), especially in which the coated film of the powder is not dissolved even under alkaline conditions, preferably for cosmetics. Additionally, no description is found with respect to a surface-treated powder which is prepared by hydrophilicaly treating the silicone resin or the organic powder (particle) by hydrophilic treatment, of which the coated film is not dissolved even under acidic and alkaline conditions and which is excellent in dispersibility and long-term dispersion stability, a dispersion and cosmetics containing the same, and the like.
Patent Document 1: Japanese Patent Kokai Publication JP-A-1-301760
Patent Document 2: Japanese Patent Kokai Publication JP-A-63-57516
Patent Document 3: Japanese Patent Kokai Publication JP-A-3-294220
Patent Document 4: Japanese Patent Kokai Publication JP-A-9-110642
Patent Document 5: Japanese Patent Kokai Publication JP-A-9-104833
Patent Document 6: Japanese Patent Kokai Publication JP-A-61-286310
Patent Document 7: Japanese Patent Kokai Publication JP-A-2003-26958
Patent Document 8: Japanese Patent Kokai Publication JP-A-9-124855